Yoshiyuki Morikawa

Bearing Capacity of Breakwater Mound Under Tsunami-Induced Seepage Flow

Water level difference induced by tsunami generates seepage flow in a mound of caisson-type breakwaters. It has been pointed out that the seepage force weakens a bearing capacity of a mound. The present paper describes bearing capacity properties of a mound under seepage flow, by using centrifuge model tests and finite element method analyses. Two types of model tests were conducted in the study: horizontal load tests and combined tests with horizontal load and seepage flow. According to the model tests, seepage force resulted in decrease of a bearing capacity. In addition, it was confirmed that finite element method analyses could simulate the model tests, and the suitable hypothetical adhesion was shown to simulate the effect of seepage force.

Physical and mechanical properties of cement-treated granular soils with respect to geotechnical application

To utilize soft clayey soils as construction materials, granulating technique is introduced. The technique converts soils dredged at ports and harbors to granular materials by adding small amounts of cement and polymer. Particle density, particle shape and particle distribution characteristics of cement-treated granulate soil (CTGS) as well as stress–strain relationships were investigated from laboratory tests. The results showed that CTGS was a lightweight material because small voids may be included in the particles. In addition, it was found that CTGS showed ductile behavior with the volume contraction when CTGS was subjected to shear deformation even if CTGS was initially prepared by compaction.

Engineering Properties of Cement–Treated Granular Soil for Geotechnical Application

This study introduces a new method to produce a granular material to encourage use of dredged materials for construction applications. Cement Treated Granular Soil (CTGS) was produced from dredged marine clay mixed with proper amounts of cement and polymer. This study focuses on lean mixture design to reduce the production cost. The applicability of CTGS as a geomaterial was verified based on engineering properties (i.e., compaction characteristics, California Bearing Ratio, compressibility, strength and deformation characteristics) obtained from laboratory tests. The principle of treatment and physical properties of CTGS are also discussed. It was found that CTGS is lightweight, has high porosity, and possesses similar characteristics to conventional granular materials. The densification is not sensitive to water content, and the strength and stiffness parameters obtained from the tests indicate that CTGS shows high potential for applications such as reclamation, subgrade, or backfill material.